1. Field of the Invention
The present invention relates to an integrated source driver and a liquid crystal display device thereof, and more particularly, to an integrated source driver and a liquid crystal display device thereof capable of integrating an external reference voltage generator and limiting generated adjustable voltage ranges of each internal reference voltage, to save hardware cost or increase voltage adjustment resolution.
2. Description of the Prior Art
Owing to the low price and high quality, liquid crystal display devices have been widely used in information products such as notebooks, Personal Digital Assistants (PDAs), Mobile phones, and watches.
A liquid crystal display device is mainly composed of single or a plurality of source drivers, single or a plurality of gate drivers and a panel. The source drivers and the gate drivers are used for controlling crisscrossing data lines and scan lines in the panel, and a thin film transistor is connected to intersections of each data line and scan line (i.e. the thin film transistors are distributed as a matrix on the panel, and each thin film transistor corresponds to a pixel). A conventional source driver needs to receive multiple external reference voltages to output a correct voltage to a data line, so as to drive a pixel of a panel of a liquid crystal display device for displaying. Therefore, reference voltages play important parts. In many applications, an additional reference voltage generator is utilized to strengthen the driving capability of the reference voltages and stabilize the reference voltages.
Besides, in a conventional panel application, the output voltages of the source drivers are changed by adjusting reference voltages, so as to adjust a screen color. Therefore, the reference voltage generator providing reference voltages to source drivers needs to be capable of adjusting to the reference voltages.
Please refer to FIG. 1, which is a schematic diagram of a conventional source driver 10 receiving positive gamma reference voltages VPR1-VPRm and negative gamma reference voltages VNR1-VNRm from an external reference voltage generator 12. As shown in FIG. 1, after the conventional source driver 10 receives positive gamma reference voltages VPR1-VPRm and negative gamma reference voltages VNR1-VNRm from the external reference voltage generator 12 and then the positive gamma reference voltages VPR1-VPRm and the negative gamma reference voltages VNR1-VNRm are processed by a positive polarity gamma correction resistor 102 and a negative polarity gamma correction resistor 104, the conventional source driver 10 outputs correct voltages to data lines for driving corresponding pixels by a digital to analog converter (DAC) and related circuits. This part is well-known for those skilled in the art, and hence is not narrated hereinafter.
In such a situation, to save a system cost and dynamically adjust reference voltages, the external reference voltage generator 12 and the conventional source driver 10 are further integrated into an integrated source driver in the prior art, such that multiple reference voltages are generated inside the integrated source driver by a single controlling method.
Noticeably, in order to adapt to different applications, each reference voltage outputted by the conventional external reference voltage generator 12 needs to be adjustable by a controlling mechanism, and the conventional external reference voltage generator 12 needs to provide rail-to-rail adjustable ranges (i.e. each reference voltage is adjustable within a supply voltage and a ground level of the external reference voltage generator 12).
However, if the conventional external reference voltage generator 12 and the conventional source driver 10 are directly integrated into the integrated source driver, and if the adjustable ranges of the reference voltages are still the same with the rail-to-rail adjustable ranges of the conventional external reference voltage generator 12 while high resolution is maintained, the hardware cost is quite large because the source driver 10 requires more reference voltages. Thus, there is a need for improvement of the prior art.